Interphase Stabilization of LiNi 0.5 Mn 1.5 O 4 Cathode for 5 V-Class All-Solid-State Batteries.

Employing high voltage cobalt-free spinel LiNi _0.5 Mn _1.5 O ₄ (LNMO) as a cathode is promising for high energy density and cost-effectiveness, but it has challenges in all-solid-state batteries (ASSBs). Here, it is revealed that the limitation of lithium argyrodite sulfide solid electrolyte (Li ₆ PS ₅ Cl) with the LNMO cathode is due to the intrinsic chemical incompatibility and poor oxidative stability. Through a careful analysis of the interphase of LNMO, it is elucidated that even the halide solid electrolyte (Li ₃ InCl ₆ ) with high oxidative stability can be decomposed to form resistive interphase layers with LNMO in ASSBs. Interestingly, with Fe-doping and a Li ₃ PO ₄ protective layer coating, LNMO with Li ₃ InCl ₆ displays stable cycle performance with a stabilized interphase at a high voltage (≈4.7 V) in ASSBs. The enhanced interfacial stability with the extended electrochemical stability window through doping and coating enables high electrochemical stability with LNMO in ASSBs. This work provides guidance for employing high-voltage cathodes in ASSBs and highlights the importance of stable interphases to enable stable cycling in ASSBs.
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